Prism-Coupled Holographic Waveguide Replication for High Spatial Frequencies
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for manufacturing volume holographic optical elements (VHOEs) face challenges in fabricating contact-copy master holograms, particularly when dealing with non-planar object and reference beams or the need for well-defined apertures, and are limited in producing holograms with high spatial frequencies due to total internal reflection constraints.
Innovation Solution
The use of composite master holograms and prism-coupled configurations allows for the formation of holograms with high spatial frequencies and enables reflection configurations, enhancing the simplicity of fabrication and quality of master holograms while overcoming previous limitations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional contact-copy methods are used to manufacture VHOEs, then the fabrication process is relatively simple, but the manufacturing precision and quality of master holograms deteriorate when dealing with non-planar beams or high spatial frequencies
Solution Approach 1:
The patent introduces a master hologram as an intermediary element that is first fabricated with high precision using conventional methods, then used to replicate multiple copy holograms. This master hologram acts as a mediator that transfers the complex non-planar beam patterns and high spatial frequency information to the copy holograms, enabling high manufacturing precision without requiring each individual hologram to be fabricated directly with those complex parameters.
Solution Approach 2:
The fabrication process is segmented into two distinct stages: (1) fabrication of a single master hologram with high precision using conventional contact-copy methods, and (2) replication of multiple copy holograms from the master. This segmentation allows the complex task of creating high-precision non-planar beam holograms to be divided into a simple master fabrication step followed by multiple replication steps, thereby improving manufacturing precision while controlling overall fabrication complexity.
2Manufacturing precision
If conventional methods are used, then total internal reflection constraints limit the maximum diffracted angle, but this limits the spatial frequency and application potential of the holograms
Solution Approach 1:
The patent changes the refractive index parameter by using a high-index substrate (such as silicon carbide with refractive index approximately 2.6) for the master hologram. This parameter change allows the diffracted beams to exceed the critical angle for total internal reflection that would limit conventional low-index substrates. By changing this fundamental material parameter, the system achieves higher spatial frequencies and broader angular ranges, thereby expanding adaptability to applications such as augmented reality displays and solar energy systems that require high spatial frequency gratings.
3Reliability
If high spatial frequency holograms are manufactured, then diffraction efficiency improves, but the fabrication process becomes more difficult due to precision requirements
Solution Approach 1:
The patent employs a copying approach where a single master hologram with high spatial frequency patterns is fabricated once with high precision, then used to replicate multiple copy holograms. This copying method ensures that the high diffraction efficiency characteristics of the master are transferred to the copies, maintaining high reliability. The fabrication ease is improved because the complex high-precision fabrication is performed only once for the master, rather than requiring the same level of precision for each individual hologram in a production run.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the reliable manufacturing of VHOEs with high diffraction efficiency, capable of forming gratings that diffract beyond the critical angle, thus expanding their application potential in augmented reality displays and solar energy systems.
Implementation Method 1
one or more prisms positioned to receive an illumination beam on a first face thereof, and a composite master HOE in contact with a second face of the one or more prisms to receive the illumination beam after propagation through the one or more prisms
Implementation Method 2
The composite master HOE includes a reference beam component and an object beam component
Implementation Method 3
a copy HOE positioned in contact with a third face of the one or more prisms to receive, upon illumination of the master HOE by the illumination beam, a holographic exposure comprising first order diffracted illumination from both the reference beam component and object beam component
Data Source
AI summary
Methods and systems are described that enable manufacturing of holograms with high spatial frequencies and allow composite master holograms to be formed in reflection configurations. An example system for replicating transmission-type holographic elements includes one or more prisms positioned to receive an illumination beam on a first face. A composite master holographic element is positioned in contact with a second face of the one or more prisms to receive the illumination beam after propagation through he one or more prisms. The composite master hologram includes a reference beam component and an object beam component. The replication hologram is positioned in contact with a third face of the one or more prisms to receive, upon illumination of the master HOE by the illumination beam, a holographic exposure comprising first order diffracted illumination from both the reference beam component and object beam component at an exposure region of the copy HOE.